302 



Transactions of the Canadian Institute. 



[Vol. VII. 



VIII. b. — Leaf of Aiiipelopsis. 



Solution. Strength. 



m/4 

 m/4 

 m/4 

 m/4 



m/4 



m/50 

 m/400 



m/4 



m/400 



Time to kill. 



4 days 



4 days plus 



4 days 



3 days 



4 days 



2 days 



4 days plus 



I day 



4 days plus 



4 days 



5 days plus 



Remarks. 



Veins darkening',' brown in streaks. 



Dead and crisp at the margin. 



Blade spotted. 



Blade spotting, wilting' and limp second day, 

 drj'ing up fourth da\'. 



Base brown, margfin green, petiole and veins 

 darkening'. 



Margin black. 



Blade wilting- some, petiole dying, marg'in 

 black, veins dying" near base of leaf. 



Frosen appearance between veins, veins de- 

 colourized. 



Slig'htly wilted. 



Wilting- on second da}'. 



Fresh. 



* In the cases in which the leaf died it became blackened after death. 



Certain solutions seemed to produce, after a few days, a translucent 

 appearance in the region between the main veins. It appeared as 

 though the intercellular spaces in this part of the leaf were injected with 

 water. On examination it was found that the cells in this region were 

 plasmolyzed. Then, from these considerations, namely that the cells 

 were plasmolyzed, that water appeared to be in the intercellular spaces, 

 and that solutions of considerable concentration were known to ascend 

 through the blade, it may be concluded that the cells in this region were 

 killed by an osmotic action, causing a loss of water to the cell. 



It was noticed that normal solutions of H._.S04 and of HCl had 

 practically the same toxic power, as might be expected, since they are 

 chemicall}' equivalent and contain the same amount of replaceable atoms 

 of hydrogen. This result does not accord with the results obtained by 

 Kahlenberg and True (1896, p. 92), who showed that 1/6400 gram- 

 equivalent solution of H2SO4 was as Toxic to Lupine radicles as 1/3200 

 gram-equivalent solution of HCl. Judging from their results and 

 conclusions, one might infer that they regarded a gram-equivalent per 

 liter solution of H._,S04 to contain twice as many ions as a gram-equiva- 

 lent solution of HCl which, however, is not the case according to 

 Mohr,* Talbot-j- and others. "* 



From the experiments here recorded it may be concluded that 

 certain salts kill the leaf by osmotic action, while others produce death 

 by chemical action. The latter may be classed as poisons and the 



* Titrimethode, p, 56. 



t Quantitative chem. anal., 1900. p. 65. 



